feat: add RandSliceFromGivenSlice function (#236)

random/random.go

@@ -186,6 +186,7 @@ func RandStringSlice(charset string, sliceLen, strLen int) []string {
 }
 
 // RandFromGivenSlice generate a random element from given slice.
+// Play: todo
 func RandFromGivenSlice[T any](slice []T) T {
 	if len(slice) == 0 {
 		var zero T
@@ -194,6 +195,35 @@ func RandFromGivenSlice[T any](slice []T) T {
 	return slice[rand.Intn(len(slice))]
 }
 
+// RandSliceFromGivenSlice generate a random slice of length num from given slice.
+//   - If repeatable is true, the generated slice may contain duplicate elements.
+//
+// Play: todo
+func RandSliceFromGivenSlice[T any](slice []T, num int, repeatable bool) []T {
+	if num <= 0 || len(slice) == 0 {
+		return slice
+	}
+
+	if !repeatable && num > len(slice) {
+		num = len(slice)
+	}
+
+	result := make([]T, num)
+	if repeatable {
+		for i := range result {
+			result[i] = slice[rand.Intn(len(slice))]
+		}
+	} else {
+		shuffled := make([]T, len(slice))
+		copy(shuffled, slice)
+		rand.Shuffle(len(shuffled), func(i, j int) {
+			shuffled[i], shuffled[j] = shuffled[j], shuffled[i]
+		})
+		result = shuffled[:num]
+	}
+	return result
+}
+
 // RandUpper generate a random upper case string of specified length.
 // Play: https://go.dev/play/p/29QfOh0DVuh
 func RandUpper(length int) string {

random/random_example_test.go

@@ -47,18 +47,15 @@ func ExampleRandFromGivenSlice() {
 	goods := []string{"apple", "banana", "cherry", "elderberry", "fig", "grape", "honeydew", "kiwi", "lemon",
 		"mango", "nectarine", "orange"}
 
-	isInGoods := false
 	result := RandFromGivenSlice(goods)
-	for _, good := range goods {
-		if good == result {
-			isInGoods = true
-			break
-		}
-	}
-	fmt.Println(isInGoods)
+	fmt.Println(result)
+}
 
-	// Output:
-	// true
+func ExampleRandSliceFromGivenSlice() {
+	goods := []string{"apple", "banana", "cherry", "elderberry", "fig", "grape", "honeydew", "kiwi", "lemon",
+		"mango", "nectarine", "orange"}
+	chosen3goods := RandSliceFromGivenSlice(goods, 3, false)
+	fmt.Println(chosen3goods)
 }
 
 func ExampleRandUpper() {

random/random_test.go

@@ -292,6 +292,46 @@ func TestRandFromGivenSlice(t *testing.T) {
 	assert.Equal(0, emtpyIntResult)
 }
 
+func TestRandSliceFromGivenSlice(t *testing.T) {
+	t.Parallel()
+	assert := internal.NewAssert(t, "TestRandSliceFromGivenSlice")
+
+	randomSet := []any{"a", 8, "王", true, 1.1}
+	repeatableResult := RandSliceFromGivenSlice(randomSet, 8, true)
+	assert.Equal(8, len(repeatableResult))
+	unrepeatableResult := RandSliceFromGivenSlice(randomSet, 8, false)
+	assert.Equal(len(randomSet), len(unrepeatableResult))
+
+	var findCount int
+	for _, v := range repeatableResult {
+		for _, vv := range randomSet {
+			if v == vv {
+				findCount++
+			}
+		}
+	}
+	assert.Equal(8, findCount)
+	findCount = 0
+
+	for _, v := range unrepeatableResult {
+		for _, vv := range randomSet {
+			if v == vv {
+				findCount++
+			}
+		}
+	}
+	assert.Equal(len(randomSet), findCount)
+
+	emptyAnyRandomSet := []any{}
+	emptyAnyResult := RandSliceFromGivenSlice(emptyAnyRandomSet, 3, true)
+	assert.Equal([]any{}, emptyAnyResult)
+
+	emptyIntRandomSet := []int{}
+	emtpyIntResult := RandSliceFromGivenSlice(emptyIntRandomSet, 3, true)
+	assert.Equal([]int{}, emtpyIntResult)
+
+}
+
 func TestRandBool(t *testing.T) {
 	t.Parallel()
 	assert := internal.NewAssert(t, "TestRandBool")